The invention relates to a cooling pipe for bar, especially for multiple strands made by the slitting process, wherein the cooling pipe is supplied with water under pressure.
In fine iron rolling mills, slit rolling and split rolling have been used for the purpose of increasing output in rolled materials of small dimensions. By a special gauging method, two shapes of equal cross-sectional area are formed from one bar and finish rolled as individual bars.
As a necessary result, two bars leave a finishing stand close together.
Cooling pipes for cooling bars have been disclosed in the following patents:
______________________________________ EP 0 064 771 PD - A 147 506 DE-OS 16 08 327 DE-OS 27 27 362 ______________________________________
A common characteristic of these cooling pipes is that they are all designed for cooling single rolled bars. A variety of methods are used for cooling bars running at close distances apart. In one variant, known cooling pipes, e.g., in accordance with
EP - 0064 771,
DD - A 147 506,
DE - A 1608 327,
are disposed as closely together as possible. In this manner bars can be cooled at a distance of about 300 to 400 mm apart.
Since the bars in split rolling usually leave the finish stand at a distance greater than 200 mm apart, this means that at least one bar has to be deflected. If the rolled material has a ribbed surface, e.g., reinforcing bars, and the cooling run is disposed immediately behind the finish stand, this results in great wear in the guiding systems and thus in elevated costs.
In the case of thin dimensions which are produced at higher rolling speeds, these deflections of the bars can be the cause of trouble.
Another variant is that the cooling pipes are staggered. In this manner the required distance between the two rolling lines can be reduced, but the length of the cooling run is doubled.
In another variant according to DE-OS 2727 362, a shorter distance between the bars can be achieved, but this variant entails a very high water consumption, and trouble occurs at higher rolling speeds as a result of excessively high retarding forces in the free pipe cross section. Thus, this variant does not satisfy the operating requirements.
It is inherent in all these systems that each cooling line is provided with a separate water feed and thus changes in the water feed due to various valve settings or leaks lead to different rates of flow and hence to different cooling conditions on the bars, which necessitates greater complication of the controls, such as separate temperature measuring apparatus and the like.
A system is also known for leading both bars in a simple manner through one of the known cooling pipes. In this manner short distances can be used between the bars, yet this procedure does not assure uniform cooling of the surface of the rolled steel to achieve a concentric cooling, and thus it results in warping of the material and ultimately in insufficient quality.
It is an object of the present invention to create a cooling pipe for cooling rolled bars, with which the advantages achieved in split rolling are not limited by the subsequent cooling process, and which will assure a safe guidance of the bar combined with uniform qualities in the cooled bars, and a cooling run of short length.